Macro lenses are generally those which can reproduce image as big as 1:1 or better. That means, that it fills the full image width with object long as sensor it self (24 or 35mm).Many manufacturers sometimes marking the lenses with 1:2 or even 1:3 as macro lenses because on 10x15cm paper it reproduces images bigger than reality.Nikon kit lens 18-55mm can focus as close as 28cm from sensor, that gives you at 55mm 1:3,2 reproduction. What it means you can see on following image, which is 1:1 crop of image captured with this lens. Spider's body in reality is about 7mm long.